REPORT FOR CONSULTATION ON THE
WASHINGTON, D.C. NATIONAL CAPITAL INTERSTATE
AIR QUALITY CONTROL REGION
U.S. Department of Health, Education, and Welfare
Public Health Service
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REPORT FOR CONSULTATION ON THE
WASHINGTON, D.C. NATIONAL CAPITAL INTERSTATE
AIR QUALITY CONTROL REGION
U.S. Department of Health, Education, and Welfare
Public Health Service
National Air Pollution Control Administration
Washington, D.C.
July, 1968
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CONTENTS
Introduction 1
Summary of Preliminary Findings 8
Engineering Evaluation 20
References 41
Appendices
A. Emission Inventory Procedure and Results A3
B. Diffusion Model Procedure and Results 56
C. Demographic Data 68
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PREFACE
The Secretary, Department of Health, Education, and Welfare, is
directed by the Air Quality Act of 1967 to designate "air quality
control regions" * to provide a basis for the establishment and
implementation of air quality standards. In addition to listing the
major factors to be considered in the development of region boundaries,
the Act stipulates that the designation of a region shall be preceded
by a consultation with appropriate State and local authorities.
The National Air Pollution Control Administration, DREW, has
conducted a study of the Washington urban area, the results of which
are presented in this report. The region boundaries proposed herein
reflect consideration of all available data, but the boundary is
subject to revision prior to formal designation within the discretion
of the Secretary, HEW, on the basis of the consultation. This report
is intended to serve as the background document for that consultation.
The National Air Pollution Control Administration (NAPCA) is
appreciative of assistance received either directly during the course
of this study or indirectly during NAPCA's previous activities in the
National Capital Area from the official air pollution agencies of the
District of Columbia and the States of Maryland and Virginia, the
Washington Council of Governments, the Northern Virginia Regional
Planning Commission, and the Metropolitan Washington Board of Trade.
* The word "region" (uncapitalized) means air quality control region
unless specifically noted otherwise. When capitalized, the word
"Region" refers to the specific air quality control region under
discussion.
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INTRODUCTION
"For the purpose of establishing ambient air
quality standards pursuant to section 108, and for
administrative and other purposes, the Secretary,
after consultation with appropriate State and local
authorities shall, to the: extent feasible, within
18 months after the date of enactment of the Air
Quality Act of 1967 designate air quality control
regions based on jurisdictional boundaries, urban-
industrial concentrations, and other factors
including atmospheric areas necessary to provide
adequate implementation of air quality standards.
The Secretary may from time to time thereafter, as
he determines necessary to protect the public health
and welfare and after consultation with appropriate
State and local authorities, revise the designation
of such regions and designate additional air quality
control regions. The Secretary shall immediately
notify the Governor or Governors of the affected
State or States of such designation."
Section 107(a)(2), Air Quality Act of 1967
THE AIR QUALITY ACT
Air pollution in most of the Nation's urban areas is a regional
problem. Consistent with the problem, the solution demands coordinated
regional planning and regional effort. Yet, with few exceptions, such
corrdinated efforts are notable by their absence in the Nation's urban
complexes.
Beginning with the Section quoted above, in which the Secretary
is required to designate air quality control regions, the Air Quality
Act presents an approach to air pollution control involving closely
coordinated efforts by Federal, State, and local governments, as shown
in Figure 1. After the Secretary has (1) designated regions, (2) published
air quality criteria, and (3) published corresponding documents on
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HEW designates
air quality
control regions.
HEW develops and
publishes ajr
quality criteria
based on scientific
evidence of air
pollution effects.
HEW prepares
and publishes
information on
available control
techniques.
States hold
hearings and
set air quality
standards in the
air quality
control regions.
HEW
reviews
State
standards.
States establish plans for implementation,
considering factors such as:
• Existing pollutant levels in the region
• Number, location, and types of sources
• Meteorology
• Control technology
• Air pollution growth trends
Implementation plans would set forth
abatement procedures, outlining factors
such as:
• Emission standards for the categories of
sources in the region.
• How enforcement will be employed to
insure uniform and coordinated control
action involving State, local, and reg-ooal
authorities.
• Abatement schedules for the sources to
insure that air quality standards will be
achieved within a reasonable time.
HEW reviews j
State implementation plans. J
I
States act to control air
pollution in accordance with
air quality standards and plans
for implementation.
Figure i. Flow diagram for State action to control air pollution on a regional basis.
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control technology and associated costs, the Governor (s) of the
State(s) must file with the Secretary within 90 days a letter of in-
tend, indicating that the State(s) will adopt within 180 days am-
bient air quality standards for the pollutants covered by the published
criteria and control technology documents and adopt within an additional
180 days plans for the implementation, maintenance, and enforcement
of those standards in the designated air quality control regions.
The iiew Federal legislation provides for a regional attack on
the problem and, at the same time, provides latitude in the form
which regional efforts can take. While the Secretary has approval
authority, the State(s) involved in a designated region assumes the
responsibility for developing an administrative p»ocedure as part of
their implementation plan. It is conceivable that informal co-
operative arrangements with proper safeguards will be adequate in
some regions, whereas in others, more formal arrangements, such as
interstate compacts may be selected. The objective in each instance
will be to provide effective mechanisms for control on a regional
basis.
PROCEDURE IN DESIGNATION OF REGIONS
Figure 2 illustrates the procedure used by the NAPCA in the
designation of an air quality control region. A preliminary de-
lineation of the region is developed by bringing together two
essentially separate studies - the "Engineering Evaluation" and the
"Urban Factors." To be successful, a region must include jurisdictions
capable of administering a coordinated control effort, and the com-
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ENGINEERING EVALUATION
Input
• Emissions
• Meteorology
• Physical Dim.
Computer
Pollutant
Diffusion
Model
Output
Iso-lntensity
Graphs
Existing Air
Quality
Sampling
Data
URBAN FACTORS
• Jurisdictional Boundaries
• Urban-Industrial Concentrations
• Cooperative Regional Arrangements
• Pattern and Rate of Growth
• Existing State and Local Air
Pollution Control Legislation & Programs
Preliminary
Delineation
of
Regions
Consultation
with State
and Local
Officials
Formal
Designation
by
Secretary-HEW
Figure 2. Flow diagram for the designation of air quality control regions.
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bination must include an area large enough to attack the air pollution
problem as a whole. The study of urban factors provides insight
as to the nature of the jurisdictions and the engineering evaluation
provides an indication of the geographical extent of the problem.
For air pollution control that is truly regional in scope, air
quality control regions must be defined to include the majority of
the pollution emissions contributing to the problem in an urban area
and must be extensive enough to encompass the majority of the pop-
ulation and property affected by pollution emanating from sources
within the area. This requirement could be generally satisfied by
individual evaluation of the major factors - the location, nature,
and quantity of pollutant emissions; the pattern of urban develop-
ment; existing air quality levels; and prevailing air pollution
meteorology. While separate consideration of these individual
factors provides useful insight on the nature of an urban area, it
does not provide any direct or dynamic indication of the extent of
influence of sources in an urban complex.
In the absence of adequate air quality data (which is the case
in most urban areas), the only recourse is to estimate air quality
levels by a constantly-evolving technique referred to as diffusion
modeling. Diffusion modeling is a semi-dynamic process in which the
air quality levels at selected locations are estimated by calculating
and adding together the weighted contribution from each of the sources,
or groups of sources, within the area under consideration. As with
most mathematical simulation approaches, the calculations are repetitive
and time-consuming, and so they are routinely carried out with the aid
of a computer.
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These steps are outlined under "Engineering Evaluation" in
Figure 2, and the box labeled "Input" describes the information
required to apply the diffusion model. This information consists
of data on the nature and quantity of the pollutants being released
and the physical location of the sources, the average depth of air
available for mixing and dilution, frequency of various wind velo-
cities (direction and speed), and physical dimensions and topography
of the urban area under study. The necessary calculations are made
with this information in the next step, labeled "Computer." The
result or "Output" of the diffusion model approach is the estimated
pattern of ground-level pollutant concentrations caused by the sources
of each pollutant within the area. Based on this information, "iso-
intensity" lines (which will usually be closed, irregularly-shaped
contours of equal concentrations) can be developed and presented in
graphic or map form. Validation of the iso-intensity graphs with
available ambient air quality data completes the engineering evalua-
tion process. These graphs help delineate geographical limits for
the extent of influence of pollution sources in a given area and, thus,
serve as a guide to the boundaries of the air quality control region.
The term "Urban Factors" encompasses all considerations of a
non-engineering or non-quantitative natuee. Several examples are
listed in Figure 2, but many other factors are considered. The
existence and extent of Standard Metropolitan Statistical Areas and
Planning Areas of the Department of Housing and Urban Development
are examples of some of the additional factors that can influence the
final delineation of boundaries in a given region.
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Based on the concept that, with some possible exceptions, it is
inadvisable to consider the inclusion of only part of a county in
a region, the study of urban factors results in a preliminary region
made up of the most reasonable combination of counties consistent
with the engineering evaluation.
The recommendation for the air quality control region for the
Washington, D.C. National Capital area and the necessary documenta-
tion make up the body of this report. The report itself is meant
to serve as the background document for the formal consultation with
the appropriate State and local authorities, and based on the
consultation, the Region boundaries suggested herein are subject to
revision within the discretion of the Secretary, HEW. Following the
consultation, the Secretary will publish the final determination of
the region in the Federal Register and notify Governors of Maryland
and Virginia and the Mayor of the District of Columbia of his
official designation.
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SUMMARY OF PRELIMINARY FINDINGS
Subject to the scheduled consultation, the Secretary, Department
of Health, Education, and Welfare, proposes to designate an air quality
control region for the Washington, D.C. Interstate National Capital
area, consisting of the following jurisdictions:
District of Columbia
In the State of Maryland;
Montgomery County
Prince Georges County
In the State of Virginia;
Arlington County
Fairfax County
Loudoun County
Prince William County
As so proposed, the Washington, D.C. Interstate National Capital Air
Quality Control Region would consist of the territorial area encompassed
by the outermost boundaries of the above counties, including the independent
cities of Alexandria, Falls Church, and Fairfax; and the territorial
area of all other municipalities as defined in Section 302 (f) of the
Clean Air Act, 42 U.S.C. 1857h (f). The proposed region is illustrated
in Figure 3.
The consideration of jurisdictional, social, and economic factors
and available demographic data influenced the selection of the proposed
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I
I
I
0 mile* lo
--fr°
i
""\
Vx
\
N Y y
\ /
y
v
•\,
c
x
\
?
Figure 3. Area proposed for inclusion in the Washington, D.C. National
Capital Air' Quality Control Region.
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10
boundaries for the Washington, B.C. Air Quality Control Region. The
geographical area suggested here is considered the most cohesive and
suitable base for the establishment of regional air pollution control
in the Washington, D.C. National Capital area.
One of the more important considerations which influenced the choice
was the existence of other governmental groupings with boundaries coexten-
sive with those recommended here. It is felt that existing boundaries,
agencies, and programs should be utilized wherever possible to aid in the
ease of administering newly-established regional programs. NAPCA's
proposed Region is coextensive with the Standard Metropolitan Statistical
Area of the Department of Commerce and its Bureau of the Census. The
Department of Housing and Urban Development has designated the same group
of jurisdictions as a Planning Area for that Department's regional purposes.
Finally, the Washington Council of Governments, whose limits coincide with
the boundaries of the proposed Region, has been designated the official
HUD Planning Agency in the Washington urban area and has in the past
worked with local elected and appointed officials on plans to control
air pollution.
The Secretary of Health, Education, and Welfare initiated an
Abatement Activity in early 1967 for the Washington interstate area to
which all jurisdictions proposed here for regional inclusion were a
party. The work conducted during the course of the Abatement Activity
provided most of the technical data upon which this recommendation for
designation of a region is based. The engineering evaluation suggests
that two of the Virginia counties, Prince William and Loudoun, are not
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11
overly involved in the pollution problem in the National Capital area
at the present time. The fact that these two counties are primarily
agricultural and rural would also mitigate in favor of their exclusion
from the Washington Air Quality Control Region. These findings were
over-ruled on the basis of their potential for economic growth and their
growing involvement in existing regional arrangements and the economic
and social life of the metropolitan Washington, D.C. urban complex. As
members of the Washington Council of Governments, the two counties have
participated in that organization's efforts to control pollution in the
Washington area and have developed working relationships with the other
jurisdictions involved.
Region boundaries, to be adequate, must provide for urban growth
and thus remain stable over a longer period of time. As shown in Table 1,
Loudoun and Prince William counties have by far the highest projected
growth rates of any jurisdictions in the Washington area. Statistics on
the start of the new housing (Table C-7 , Appendix C) substantiate the
expected population trends within the area. There was a 600-fold increase
in the number of housing starts in Prince William County in the 5-year
period 1962 through 1966 over the 1950 through 1954 period. The similar
statistic for Loudoun County is 392 per cent, over twice the next highest
rate of increase (Prince Georges County).
Comparison of 1965 population distribution (Figure 4) and employment
distribution (Figure 5) illustrates the dependence of suburbanites on
urban employment. There is also an obvious outward trend in population
distribution predicted for the 1965-2000 period (Figure 6), whereas there
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Table 1. Percentage Growth Rates by Jurisdiction, 1940-2000.
County or City
District of Columbia
tontgomery Co.
Prince Georges Co.
Alexandria City
Arlington Co.
Fairfax Co.
Fairfax City
Falls Church
Loudoun Co.
Prince William Co.
Past and Projected Growth Rates, per cent
1940-1950
21.0
95.9
116.2
84.5
137.0
141.0
99.0
192
4.2
27
1950-60
-5.0
107.6
84.2
42.5
20.6
152.5
600.0
22
16
122
1960-70
9.0
49.0
74.8
61.5
20.8
70.0
81.0
17
75
120
1970-80
6.5
34.0
32.8
23.7
9.2
44.0
47.0
8.3
86
81
1960-80
16
100
132
100
32
147
165
28
226
300
1970-2000
16
95
91
52
28
139
84
25
306
261
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SOURCE: THE REGIONAL DEVELOPMENT GUIDE I966-500O
•Y THE NATIONAL CAPITAL REGIONAL PLANNING COUNCIL
">•
Figure 4.
«*••
1965 POPULATION DISTRIBUTION
WASHINGTON METROPOLITAN AtEA
REGIONAL OVERLAY SERIES
MdROPutlTAN WASHINGTON COUNCIL OF GOVERNMENTS
Ul
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N
I
ml r*orx>i •*•••* *.--., TLJ* . • •. •
1 DOT EQUALS 100 PERSONS
:.-,/ I96S DISTRIBUTION
SOURCE THE REGIONAL OEVEIOPMENT GUIDE 1966-2000
•Y THE NATIONAL CAPITAL REGIONAL PLANNING COUNCIL
Figure 5. 1965 EMPLOYMENT DISTRIBUTION
WASHINGTON METROPOLITAN AREA
REGIONAl OVERLAY SERIES
METROPOLITAN WASHINGTON COUNCIL Of GOVERNMENTS
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1 DOT EQUALS 100 PERSONS
•3fe- POPULATION INCREASE 1965-2000
POPULATION DECREASE 196S-2OOO
SOURCE: THE REGIONAL DEVELOPMENT GUIDE 1966-2000
BY THE NATIONAL CAPITAL REGIONAL PLANNING COUNCIL
Figure 6.. 1965-2000 change in POPULATION DISTRIBUTION
WASHINGTON METROPOLITAN AREA
REGIONAL OVERLAY SERIES
METROPOLITAN WASHINGTON COUNCIL OF GOVERNMENTS
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16
appears to be no such trend in employment distribution during that
period /Figure 7). This suggests that the dependence of people in the
suburbs on the central city will increase, leading to a more cohesive
region in the future.
Figure 8 illustrates the existing major transportation system for
the region, and again, Loudoun and Prince William counties appear as
satellites to the urban area. All future plans for transportation
facilities include provisions for the expected growth of these two counties.
The location of Dulles International Airport in Loudoun County is expected
to lead to increased expansion in that area, both residential and industrial.
The Northern Virginia Regional Planning and Economic Development
Commission has developed a regional plan for the four Virginia counties
and associated independent cities. The Commission plans for the year 2000
(Figure 9) envision land-use and associated transportation systems. The
expected role of Loudoun and Prince William counties as sites for residen-
tial, commercial, and indistrial development, all of which will be closely
associated with the more centralized portion of the Washington, D. C.
urban area, are illustrated in this plan.
In short, the factors mentioned above all point out the cohesive
nature of the region proposed here as to its social and economic make up.
The next section illustrates the geographical nature of the area's air
pollution and demonstrates that the region boundaries suggested here are
sufficiently encompassing to provide for a truly regional attack on
the problem.
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Figure 7. 1965-2000. change in EMPLOYMENT DISTRIBUTION
1 DOT EQUALS 100 PERSONS
vi, EMPLOYMENT INCREASE I96S-2OOO,
EMPLOYMENT DECREASE I96S
SOURCE- THE REGIONAL DEVELOPMENT GUIDE 1966-20OO
BY THE NATIONAL CAPITAL REGIONAL PLANNING COUNCIL
REGIONAL OVERLAY SERIES
METROPOLITAN WASHINGTON COUNCIL Of GOVERNMENTS
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N
(
\
AIRKXTTS
CAMIE*
C CONTINtNTAI
I INTEKONTINfNTAl
GCNERAL AVIATION
S SECONDARY
N NA(VFt)
L LOCAL
T TRUNK
M MILITARY
H HELIPORT
MAJOR HIGHWAY SYSTEMS
RAILROAD
-• PASSENGER TERMINAL
A MARINE FACILITIES
OUUU IMrfltlAU
J"'
v
Figure 8. 1965 Major Transportation System
V (source: Metropolitan Washington
Council of Governments)
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residential, commercial,
or industrial land use.
• state boundary
, _ county boundary
_ major freeway
Figure 9. Northern Virginia Regional Planning
Commission Year 2000 Plan.
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ENGINEERING EVALUATION
The engineering evaluation is based on a study of pollutant emissions,
meteorology, available ambient air quality data, and air quality levels
as estimated on the basis of diffusion model calculations. The Technical
Report^ previously conducted for the Washington, B.C. Abatement Action
served as a major reference during this study.
Evaluation of all data available for the Washington area including
the diffusion model results, indicates that the region should include
at least Montgomery and Prince Georges counties in Maryland; the District
of Columbia; Fairfax and Arlington counties in Virginia; and the independent
Virginia cities of Fairfax, Falls Church, and Alexandria. As was indicated
in the summary section of this report, the above conclusion prevailed
with the exception that Loudoun and Prince William counties in Virginia
have been proposed for inclusion in the region, not because of their
present involvement in the area's air pollution problem, but because of
their growth pattern and what it portends for the future. The factors
leading to the above conclusion are discussed below.
EMISSION INVENTORY RESULTS
The emission inventory conducted for the Abatement Action^ included
estimates for emission of five major pollutants - particulates, sulfur
oxides, carbon monoxide, nitrogen oxides, and total hydrocarbons. Table 2
summarizes the results from the more in-depth discussions of the emission
inventory technique and results, presented in Appendix A of this report.
Emissions are listed in Table 2 for sulfur oxides, carbon monoxide,
and particulates, with totals shown for each of the major jurisdictions
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Table 2. Mean Day Emissions for Various Averaging Times
(Tons)
County or City
District of Columbia
Montgomery Co.
Prince Georges Co.
Maryland Subtotal
Arlington Co.
Fairfax Co.
Loudoun Co.
Prince William Co.
Alexandria City
Virginia Subtotal
Area Totals
Sul
Annual
175
189
179
368
22
17
2
43
63
147
690
fur Diox
Winter
281
208
202
410
49
38
3
43
65
198
889
ide
Summer
90
177
198
375
4
3
-
43
62
112
577
Car
Annual
978
602
698
1,300
282
521
57
122
188
1,170
3,448
:>on Monc
Winter
861
530
614
1,144
248
458
50
107
165
1,028
3,033
xide
Summer
1,046
644
747
1,391
302
557
61
131
201
1,252
3,689
Pa
Annual
30
18
21
39
5
7
1
7
6
26
95
rticulates
Winter
43
20
24
44
8
12
1
7
7
35
122
Summer
25
17
22
39
4
6
1
7
6
24
88
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in the area. Tables A-l through A-4 in Appendix A provide a breakdown
by individual emission zones. These three pollutants were chosen because
of their representativeness of the major pollutant source categories.
The estimate of sulfur oxide pollution levels illustrates the impact of
fuel-burning activities (where almost 70% of the sulfur pollution comes
from the burning of coal) at private, commercial, or government-owned
power plants. Carbon monoxide pollutant levels provide the best indica-
tion of the impact of motor vehicles on the regional air pollution
pattern, since 98 per cent of all carbon monoxide emitted in the Washington
area comes from motor vehicles. Diffusion model estimates of suspended
particulate levels provides the best measure of the combined impact of
all pollutant source categories, since, of the five pollutants covered
in the emission inventory, particulate emissions are the most evenly-
distributed by source category (no single source category accounts for
more than 28 per cent of the total).
The second and perhaps more important reason for confining the
diffusion model work to these three pollutants is the use and interpre-
tation of the results. By predicting the patterns of dispersion of a
few major pollutants, the diffusion model work provided a guide to the
desirable extent of the region but did not dictate the exact boundary
location. By way of example, if significant levels of one or more of
the three pollutants extend into a county contiguous to the major
urbanized area, this would be an indication that that county is being
subjected to a pollutant load that constitutes a part of the total-area
problem, and that the county should be considered for inclusion in the
air quality control region. The final decision is then made by bringing
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into consideration the involvement of that county in the overall activities
of the urban area.
The total quantity of pollutants emitted in each of the reporting
zones was converted to daily emissions under minimum, average, and maximum
space-heating conditions and related to the land area of each zone. The
resulting emission densities are presented graphically in Figures 10, 11,
and 12 for an average space-heating day in tons per square mile per day.
The pattern of emission densities for each of the three pollutants
are closely related to the pattern of urbanization in the central part
of the area. The maximum emission densities occur in or close to the
District of Columbia, but the density pattern in each case extends well
into Montgomery and Prince Georges counties in Maryland and Fairfax
County in Virginia. The emission density patterns for sulfur oxides
and particulates are complicated by the existence of three major point
sources outside of the highly urbanized area but still within the 6-county
area. Figure 13 shows the location of these 3 major sources (northwestern
Montgomery County, southeastern Prince William County, and southeastern
Prince Georges County) as well as all other sources in the area emitting
more than 100 tons per year of any single pollutant.
DIFFUSION MODEL RESULTS
While the geographical distribution of pollutant sources illustrates
clearly the core of the air quality control region, it does not, by itself,
provide any insight as to the extent of influence of the combined sources
on the people and property located outside of the highly-urbanized portion
of the greater Washington, D.C. complex. A study of air quality levels
known or estimated to occur is useful in determining the area affected
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24
Figure 10- Sulfur oxides emission densities for an average
space-heating day.
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25
Figure 11. Carbon monoxide emission densities for an average
space-heating day.
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26
Figure 12- Participate emission densities for an average
space-heating day.
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27
• POINT SOURCES EMITTING
MOM THAN 100 TONS PCI YEAR
OF ANY SINGLE POLLUTANT
A POINT SOUICES EMITTING
MORE THAN 1000 TONS PER YEAR
Of ANY SINGLE POLLUTANT
Figure 13. Point sources that emit 100 tons or more per year of
a single pollutant.
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28
by the pollution sources and thus subject to inclusion in the air quality
control region. Such analyses can be based directly on air quality samp-
ling data in those instances where the sampling program covers a large-
enough area and has been in existence long enough to provide reliable
patterns of air quality throughout the region under study. Unfortunately,
such air quality data rarely exists, and it becomes necessary to develop
estimates of prevailing air quality. The diffusion model is the technique
by which such estimates are madii on the basis of information on pollutant
emissions, meteorological conditions, and the physical character of the
urban complex. The diffusion model used in this study and the results
obtained are covered in detail in Appendix B and summarized briefly
below.
The model is based on the long-term Gaussian diffusion equation,
described by Pasquill ^ and modified in recent years^» ? for application
to the multiple-source situation of an urban complex. The basic equation
assumes that the concentration of a pollutant within a plume has a
Gaussian distribution about the plume centerline in the vertical and
horizontal directions, with the standard deviations (
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29
and Figure 14 show the meteorological data required to apply the model
for each of the three time periods. The mixing depths for the three
time periods were derived as the average of the mean morning and afternoon
readings, as shown in Table 3. Figure 14 shows the percent frequency
of occurrence of surface wind direction from 1951 through 1960 at
Washington National Airport for summer, winter, and annual averages.
Combined with data on surface wind speed, this information is used in
the diffusion model to weight the distribution of pollutant emissions on
the 16 points of the compass.
Table 3. Average mixing depths for Washington, D.C. by season.
Season
Winter
Summer
Annual
Mixing Depths, meters
Morning
Average
539
378
439
Afternoon
Average
963
1884
1503
Average, morning
and Afternoon
752
1131
971
Using the foregoing information on emissions and meteorology,
concentrations were calculated for each of the three pollutants for each
of the three time periods at a total of 97 ground-level receptor points
(20, 30, 40, 50, 70, and 100 kilometers from an assumed center point at
16 compass directions, plus an estimate of the concentration at the
center point itself).
The results are presented in Figures 15, 16, and 17. Figure 15
shows the average concentrations of S02 expected to occur during the three
winter months. Figures 16 and 17 illustrate similar results for CO and
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30
12
WINTER
Figure 14. Percent frequency
of wind direction for various
averaging times, based on
1951-60 data from Washington's
National Airport.
II
ANNUAL
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suspended particulates, respectively. The results for the latter two,
however, are based on annual rather than winter conditions, since these
conditions gave higher estimates of concentration than the other averaging
times considered.
SULFUR DIOXIDE
Figures 1-3 in Appendix B shows the results of the diffusion model
calculations for S02. Comparison with sampling data (Figure 15) suggests
that the model over-estimates concentrations of this pollutant. This
tendency to over-estimate S02 concentrations was assumed to result from
the inability of this model in its present state to account for the
degradation of S02 in the atmosphere into other sulfur compounds. Figure
15 incorporates a modification of the initial output of the model by
applying an exponential decay factor involving an arbitrarily-assumed
6-hour half life. Comparison of the diffusion model results (as modified)
with available monitoring data show the estimates to fall well within
a factor of two of the measured concentrations.
The concentrations predicted by the model are interpreted generally
as "above background" levels, since the model is not supplied with infor-
mation on sources of the pollutant outside of the area initially surveyed.
This is not considered an important factor with respect to S02, however,
since background levels are generally low compared to the levels found
in urban areas. The concentrations presented in Figure 15 can be viewed
for the purposes of this report then as total S02 concentration.
Concentration contours are presented in Figure 15 down to a
concentration of 0.01 ppm, the concentration at which human health effects
-------
SO., - ppm
32
0.01
Aerometric Data
(above table)
STATION
A
B
C
D
E
F
G
CONCENTRATION ,
0.05
0.05
0.04
0.03
0.05
0.06
0.05
ppm
Figure 15. Estimated average winter day concentrations of SO in
ppra. Includes an assumed 6-hour half-life.
-------
33
begin to occur. This contour line encloses all of the District of
Columbia, Alexandria, Falls Church, Arlington County and Prince Georges
County; most of Montgomery and Fairfax counties; and small portions of
Loudoun County in Virginia and 5 bordering counties in Maryland. The
encroachment of the 0.01 ppm contour into the 5 bordering Maryland
counties has been discounted for one of two reasons: 1) two of the
counties - Howard and Anne Arundel - are more intimately involved in the
Baltimore than in the Washington urban area; 2) except for two large
point sources of S02, the remaining three counties - Frederick, Calvert,
and Charles - would be essentially unaffected by Washington area SC>2
sources. The Maryland portion of the region boundary would thus be
coterminous with the outer reaches of Montgomery and Prince Georges
counties. This decision is consistent with the recent regulation of the
State of Maryland, in which these two counties were established as a
region for air pollution control purposes.
CARBON MONOXIDE
The results of the diffusion model estimates of carbon monoxide
concentrations on an annual basis are presented in Figures 4-6 in Appendix
B. Aerometric data plotted on the same Figure indicate that the model
routinely estimates concentrations 2 to 5 times lower than those reported
at actual sampling sites. For the purpose of showing the pattern of CO
levels, the model estimates are adequate; but choosing a cut-off level
that has relevance in terms of those values routinely reported from
sampling and those to be covered in the future criteria document is
difficult because of the 2-5 factor mentioned above. The diffusion
model does not reflect the built-up nature of the area in which most of
-------
34
the CO is emitted and thus assumes that the pollutant has more immediate
space and volume within which to disperse. Until the air into which the
pollutant is being emitted moves away from the built-up part of the
urban area, the pollutant is channeled through streets and around build-
ings. This fact is assumed to cause most of the discrepancy between
estimated and measured concentrations of CO.
Based on the 2-5 difference, an average factor of 3.5 was applied
to the diffusion model estimates to give "equivalent" CO concentrations.
The resulting estimate of CO levels is shown in Figure 16. Contours have
been plotted for 6, 4, 2, and 1 ppm of the pollutant. The results are
shown only for annual conditions since there is little seasonal variation
in the rate of CO emissions. Available information on CO indicates that
an annual average concentration of one part per million is indicative
of conditions which begin to affect people. Using this level as a guide
to the region boundary, we arrive at essentially the same conclusion
as in the case of S02- Even though the 1 ppm CO contour is slightly
less encompassing that the 0.01 ppm S02 contour, they both suggest that
the same major jurisdictions should be included in the region.
The results for CO reflect the prevailing wind direction toward the
northeast, raising the question fo the relative air pollution impact of the
Washington and Baltimore urban centers on each other and the possibility
that they should be combined into one air quality control region. Diffusion
model estimates of CO concentrations were chosen as a means to evaluate
this possibility. An emission inventory for CO was conducted for the
Baltimore urban area and subjected to diffusion model calculations extend-
ing to the center of the Washington, D.C. urban area. On an annual average
-------
35
CO - ppm
Figure 16. Equivalent carbon monoxide concentrations based
on average annual emission levels.
-------
36
basis, only one per cent of the CO measured at downtown Washington is
predicted to come from Baltimore sources. In like manner, less than
7 per cent of the CO measured in Baltimore is predicted to emenate from
Washington area sources.
It is recognized that under more critical, short-time-period
meteorological conditions, the impact of these two urban areas on each
other would be greater than that predicted on an annual average basis,
but the designation of regions large enough to encompass the problem
area during the less frequent occurrence of the higher concentrations
would place undue hardship on the administering agency. Day-to-day air
pollution control efforts in a region defined on the basis of long-term
average conditions will tend to reduce the impact of sources in the
region on the surrounding area. The "overlap" left untouched by this
approach is more appropriately left to coordination between adjoining air
quality control regions. The implementation plans of proximately-located
air quality control regions should provide this needed coordination as
part of their emergency action procedures.
There will always be a likelihood of sources of pollution just
beyond the boundary selected for the region that contribute to air pollu-
tion levels in the region. As considerable as the impact of such a
source might be, it may not warrant the inclusion of an additional whole
county in the region. This situation should be treated whenever it occurs
in the implementation plans for the region being affected by the source(s).
SUSPENDED PARTICULATES
The diffusion model estimates of suspended particulate concentrations
are presented in Figure 17. However, the results do not include an
-------
37
Suspended Particulates- g/M"
50
Figure 17. Estimated annual average concentrations of suspended
particulates, above background, no deposition.
-------
38
allowance for background concentra.tions, and they are based on an emission
inventory that estimates total particulate emissions. The first would
cause the model estimates to be lower than measured concentrations, and
the second would cause the estimates to be higher than measured concen-
trations of suspended particulates. The close correlation between the
model estimates and measured concentrations (Table 4) suggests that the
two factors not incorporated in Figure 17 essentially compensate one
another.
Although the results from the model calculations can be interpreted
literally, they are just as meaningful for our purposes when interpreted
in a relative sense. In Figure 18, the "relative" concentrations are
plotted versus location along the east-west and the north-south axes of
the urban area; also shown are the boundary locations along the axes for
the jurisdictional entities. The graph for the north-south axis shows
that the relative impact of particulate pollution sources within the
region is insignificant at the outer edge of Prince Georges County to the
south and Montgomery County to the north. Similarly, the east-west
concentration profile shows that the relative impact is insignificant at
the outer edge of Fairfax County to the west and Prince Georges County
to the east. Taken together, these findings suggest that the Maryland
counties of Montgomery and Prince Georges, the Virginia counties of
Arlington and Fairfax, the Virginia cities of Fairfax, Falls Church, and
Alexandria should be included in the air quality control region along
with the District of Columbia. This conclusion is consistent with those
based on S02 and CO analyses.
-------
Table 4. Relationship of diffusion model results
for suspended particulates to aerometric
data.
39
Station
Number3
14
15
21
33
41
46
58
59
Location
Cheverly
Hyattsville
Alexandria
CAMP
Nat'l Airport
Seven Corners
NIH
Suitland
*3
Concentration, mg/M
Estimated
70
70
65
100
78
58
60
70
Measured
78
97
70
101
71
61
65
86
Ratio,
Estimated
to Measured
0.90
0.72
0.93
1.00
1.10
0.95
0.93
0.82
Average Ratio = 0.92
See Reference 3 for exact location
-------
Relative Concentration
Howard County
Anne Arundel County
Montgomery County
Prince Georges
County
District of
Columbia
District of
Columbia
Arlington
Falls Church
Prince Georges County
Charles County
Fairfax County
Loudoun County
Prince William County
Figure 18
Relative concentration
of suspended particulates
on the major axes center
geographically on
Washington, D.C.
uo
Relative Concentration
-------
References
1. Clean Air Act, 42USC 1857 et. seq. Section 107 (a) (2)
2. Statistics - Washington Metropolitan Area. Metropolitan Washington-
Council of Governments, Washington, D. C., pp. 138-9. January, 1968.,
3. Technical Report, Washington, D. C. Metropolitan Area Air Pollution
Abatement Activity USDHEW, PHS. November, 1967.
4. Technical Report, Washington, D. C. Metropolitan Area Air Pollution
Abatement Activity. USDHEW, PHS. pp. 54-97, and C-l through C-12.
November, 1967
5. Pasquill, F. The estimation of the dispersion of windborne material,
Meteorology Magazine, 90: 33-49. 1963.
6. Turner, D. B.; Workbook of Atmospheric Dispersion Estimates. PHS
Publication No. 999-AP-26, 84 -pp. National Center for Air Pollution
Control, Cincinnati, Ohio. 1967.
7. Martin, D. 0., A general atmospheric diffusion model for estimating
the effects on air quality cf one or more sources; Paper No. 68-148,
61st Annual Meeting, APCA, St. Paul, Minnesota. June, 1968.
8. Technical Report, Washington, D. C. Metropolitan Area Air Pollution
Abatement Activity. National Center for Air Pollution Control, DHEW.
Cincinnati, Ohio. pp. 11-20. November, 1967.
9. U. S. Weather Bureau data.
10. Technical Report, Washington, D. C. Metropolitan Area Air Pollution
Abatement Activity. National Center for Air Pollution Control, DHEW.
Cincinnati, Ohio. pp. 27-36. November, 1967.
11. Air Quality Criteria for Sulfur Oxides. PHS, DHEW, March, 1967.
-------
APPENDICES
Appendix A. Emission Inventory Procedure and Results
Appendix B. Diffusion' Model Description & Results
Appendix C. uemograpnic Data
-------
43
APPENDIX A. EMISSION INVENTORY PROCEDURE
The recent conduct of an emission inventory as part of the
Washington, D.C. Interstate Abatement Action provided the information
on emissions necessary to study the area prior to the designation of an
air quality control region. The initial data were compiled during the
2-month period from February through March 1967. The Public Health
o
Service rapid survey technique for emission inventories was used. The
inventory consisted of evaluating the consumption of gasoline, diesel
fuel, coal, fuel oil, and natural gas and of determining emissions from
refuse incineration, process industries, auto burning, aircraft flights,
and evaporative losses. Emissions were determined directly from the
fuel imput to the equipment for both automotive and stationary sources.
Control equipment was also taken into account for emissions from coal
combustion and process sources. Emission factors arid average sulfur
and ash contents are listed in table A-9. The general emission factors
used were obtained from Public Health Service and New York State publi-
cations » and from various PHS staff estimates.
Annual consumption of all fuels and annual process emissions in
each zone were determined for the years 1965 and 1966. Daily emissions
were calculated for minimum, average, and maximum space-heating days and
are reported in tables A-l through A-4 as tons of pollutant per square
mile. Tables A-5 through A-7 summarize the estimates of annual emissions
of sulfur oxides, carbon monoxide, and particulates by source category
and political jurisdiction.
The emission data were converted to show mean-day emissions for
annual, winter, and summer seasons (Table A-8) to facilitate diffusion
-------
model calculations of mean-day concentration for each of the three seasons.
The conversion was accomplished by apportioning variable emissions to each
of the seasons in accordance with information on monthly heating-degree
days and then calculating the average-day emissions for each season.
-------
Figure A-l.. Emission Inventory zones.
-------
Table A-l
Emission Densities on Minimum, Average, and Maximum Space-Heating Days for District of Columbia
Zone
DC-1
DC-2
DC -3
DC-4
DC-5
DC-6
DC -7
DC-8
DC -9
DC-10
DC-11
DC-12
DC-13
DC-14
DC-15
DC-16
DC-17
DC -18
DC-19
DC-20
DC-21
DC-22
Area,
mi^,
0.7
0.7
0.8
0.6
0.8
1.1
1.0
1.4
3.5
2.0
7.0
3.3
5.6
1.1
1.4
6.4
2.4
5.0
5.6
1.8
5.2
4.0
Sulfur oxides,
tnns/Hav-Tni 2
Min.
0.2
0.8
0.3
0.5
0.7
0.9
0.5
1.0
0.3
0.1
6.1
0.1
Neg.
0.1
25.9
0.1
0.2
0.1
0.4
0.2
0.1
Neg.
Ava.
6.1
4.5
2.4
10.3
12.8
2.2
4.7
5.4
4.5
4.5
5.8
1.2
1.0
3.1
22.3
2.7
10.3
0.8
2.3
1.5
1.3
1.8
Max.
8.5
8.7
6.6
24.0
30.1
14.5
10.6
11.6
10.5
10.8
7.5
2.8
2.3
6.6
37.3
6.3
24.6
1.8
5.0
3.2
3.0
4.1
Participates,
tnn<;/rlav-TTn 2
Min .
0.3
0.4
0.3
0.7
0.5
0.4
0.4
0.2
0.3
0.2
2.2
0.1
0.1
0.2
2.6
0.1
0.1
0.1
0.1
0.1
0.1
0.4
Ava.
1.0
0.9
0.6
1.3
1.3
1.0
0.6
0.8
0.6
0.4
2.1
0.2
0.1
0.5
3.1
0.2
1.1
0.1
0.2
0.3
0.1
0.5
Mav .
1.9
1.5
0.8
2.2
2.3
1.9
1.0
1.3
1.0
0.7
2.2
0.3
0.2
0.9
4.5
0.5
2.4
0.2
0.3
0.6
0.2
0.6
Carbon monoxide
trvn«;/r1ay-Trn 2
Ava .
48.3
33.2
53.7
106.9
87.9
48.1
63.0
21.4
16.1
19.8
16.0
5.0
8.4
14.5
19.9
6.8
22.4
7.2
9.0
11.8
8.0
10.3
-------
Table A-2
Emission Densities on Minimum, Average, and Maximum Space-Heating Days for
Montgomery and Prince Georges Counties
Zone
M-l
M-2
M-3
M-4
M-5
M-6
M-7
M-8
M-9
M-10
>G-1
>G-2
>G-3
>G-4
>G-5
>G-6
>G-7
>G-8
>G-9
>G-10
>G-11
>G-12
>G-13
Area,
nu/
169.2
119.8
25.4
27.0
100.3
10.5
11.7
8.3
6.6
7.7
69.2
126.2
101.3
78.6
20.0
0.7
25.9
3.0
28.4
11.0
5.8
6.0
11.7
Sulfur oxides,
1-rm^/rlav-mi 2
Min
1.0
Neg.
Neg.
0.1
Neg.
0.1
0.1
0.1
0.2
0.1
3.0
Neg.
Neg.
Neg.
Neg.
0.2
Neg.
0.2
Neg.
0.1
0.2
0.2
0.1
Aim
1.0
Meg.
0.1
0.2
Neg.
0.3
0.1
0.3
0.8
0.9
2.0
0.1
Neg.
0.2
0.1
1.9
0.3
0.7
0.1
0.5
0.7
0.9
0.6
M?y
1.0
0.1
0.2
0.4
Neg.
0.6
1.3
0.7
1.8
2.0
1.6
0.1
Neg.
0.3
0.3
4.3
0.6
1.4
0.2
1.1
1.4
1.9
1.5
Particulates,
tnn^/Hflv-mi 2
Min
0.1
Neg.
Neg.
0.1
Neg.
Neg.
0.1
Neg.
0.1
0.1
0.1
Neg.
Neg.
Neg.
Neg.
0.1
Neg.
0.1
0.1
0.2
0.1
0.1
Neg.
Avo
0.1
Neg.
Neg.
0.1
Neg.
0.1
0.1
0.1
0.2
0.1
0.1
Neg.
Neg.
Neg.
Neg.
0.2
Neg.
0.2
0.1
0.2
0.2
0.2
0.4
MHY
0.1
Neg.
Neg.
0.1
Neg.
0.1
0.2
0.1
0.3
0.2
0.1
Neg.
Neg.
0.1
0.1
0.5
0.1
0.3
0.1
0.2
0.2
0.3
0.7
Carbon monoxide,
tnn<; /day-mi ^
Avc ,
0.2
0.3
1.3
4.7
1.0
3.7
5.7
4.7
10.0
7.2
0.3
0.5
0.5
0.9
4.3
8.3
3.8
5.2
3.1
6.6
10.0
6.5
3.6
-------
Table A-3
Emission Densities on Minimum, Average, and Maximum Space-Heating Days for Arlington,
Fairfax, Loudoun, and Prince William Counties
Zone
A-l
A-2
A-3
A-4
F-l
F-2
F-3
F-4
F-5
F-6
L-l
L-2
L-3
L-4
L-5
L-6
PW-1
PW-2
PW-3
PW-4
PW-5
pW-6
Area
mi2
9.8
4.4
7.5
4.1
185.1
84.2
14.9
21.1
23.2
63.0
64.0
67.0
72.0
80.5
107.0
128.0
56.0
Sulfur oxides,
tons/day-mi2
Min.
Neg.
0.3
0.3
0.1
Neg.
Neg.
Neg.
Neg.
0.1
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
71.0 [Neg.
55.6 [0.8
0 . 0 Weg .
67.0 pfeg.
48 . 0 Neg .
Avg.
0.4
2.0
1.7
2.1
Neg.
Neg.
0.2
0.1
0.3
0.2
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
0.8
Neg.
Neg.
Neg.
Max.
0.8
4.4
3.5
4.8
Neg.
0.1
0.5
0.2
0.7
0.4
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
0.8
Neg.
Neg.
Neg.
Particulates,
tons/day -mi2
Min.
Neg.
0.1
0.3
0.3
Neg.
Neg.
Neg.
Neg.
0.1
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
0.1
Neg.
Neg.
Neg.
Avg.
0.1
0.3
0.3
0.6
Neg.
Neg.
Neg.
Neg.
0.1
0.1
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
0.1
Neg.
Neg.
Neg.
Max.
0.2
0.4
0.4
1.1
Neg.
0.1
0.1
Neg.
0.1
0.1
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
Neg.
0.1
Neg.
Neg.
Neg.
Carbon monoxide,
tons/day-mi2
AVg.
4.2
11.8
. 28.9
27.5
0.5
1.0
2.2
2.2
3.8
1.5
0.2
0.1
0.1
0.2
0.1
0.1
0.3
0.4
0.3
0.4
0.5
0.2
CD
-------
Table A-4
Emission Densities on Minimum, Average, and Maximum Space-Heating Days for Cities of
Alexandria, Fairfax, and Falls Church
tone
AL-1
AL-2
AL-3
FAX-1
FC-1
Area,
mi ^
9.0
1.5
5.2
2.6
L 2.0
Sulfur Oxides,
tons/day -mi 2
Min.
0.2
0.3
11.5
0.1
0.1
Avg.
1.0
2.2
9.9
0.5
0.2
Max.
2.1
4.9
11.1
0.9
0.9
Par
ton
Min.
0.3
0.3
0.5
0.2
0.1
ticulates ,
5 /day -mi ^
Avg.
0.3
0.5
0.5
0.3
0.2
Max.
0.5
0.7
0.6
0.4
0.3
Carbon monoxide ,
tons/day -mi ^
Avg.
7.6
36.8
12.7
26.6
13.5
VO
-------
Table A-5
SULFUR OXIDE (SOX)3 EMISSIONS IN WASHINGTON, D. C. METROPOLITAN AREA, 1965 - 1966
TONS/YEAR
COUNTY OR CITY
District of Columbia
Montgomery County
Prince Georges County
Maryland Subtotal
Arlington County
Fairfax County b
Loudoun County
Prince William County
Alexandria City
Virginia Subtotal
Area Total
GRAND
Total
60,412
69,160
63,656
132,816
7,917
8,670
512
15,850
20,940
53,889
247,117
EMISSIONS BY SOURCE CATEGORY
FROM FUEL BURNING
RESIDENTIAL
10,372
3,598
4,349
7,947
3,586
1,807
211
251
2,037
7,892
26,211
COMMERCIAL &
GOVERNMENTAL
31,034
4,961
7,116
12,077
3,784
5,502
201
285
1,781
11,553
54,664
INDUSTRIAL
1,662
1,157
1,510
2.667
143
732
30
34
348
1,287
5,616
POWER PLANTS
15,711
58,555
49,866
108,421
15,123
16,494
31,617
155,749
TRANSPORTATION
1,233
684
776
1,460
310
593
62
139
213
1,317
4,010
REFUSE DISPOSAL
(ALL CATEGORIES)
400
205
39
244
94
36
8
18
67
223
867
Reported as sulfur dioxide
Includes cities of Fairfax and Falls Church, Virginia
-------
Table A-6
CARBON MONOXIDE (CO) EMISSIONS IN WASHINGTON, D. C. METROPOLITAN AREA, 1965 - 1966
TONS/YEAR
COUNTY OR CITY
District of Columbia
Montgomery County
Prince Georges County
Maryland Subtotal
Arlington County
Fairfax County8
Loudoun County
Prince William County
Alexandria City
Virginia Subtotal
Area Total
GRAND
TOTAL
357,074
219,846
254,625
474,471
102,964
190,284
20,689
44,641
68,553
427,131
1,258,676
EMISSIONS BY SOURCE CATEGORY
FROM FUEL BURNING
RESIDENTIAL
770
407
491
898
93
67
9
13
146
328
1,996
COMMERCIAL &
GOVERNMENTAL
1,133
228
204
432
166
697
15
5
92
975
2,540
INDUSTRIAL
13
7
9
16
1
11
Neg.
Neg.
2
14
43
POWER PLANTS
123
348
326
674
206
199
405
1,202
TRANSPORTATION
349,664
218,527
252,423
470,950
102,108
188,824
20,585
43,679
67.117
422,313
1,242,927
REFUSE DISPOSAL
(ALL CATEGORIES)
5,371
329
1,172
1,501
596
685
80
738
997
3,096
9,968
Including the cities of Fairfax and Falls Church
-------
Table A-7
PARTICULATE EMISSIONS IN WASHINGTON, D. C. METROPOLITAN AREA, 1965 - 1966
TONS/YEAR
COUNTY OR CITY
District of Columbia
Montgomery County
Prince Georges County
Maryland Subtotal
Arlington County
Fairfax County
Loudoun County
Prince William County
Alexandria City
Virginia Subtotal
Area Total
GRAND
TOTAL
11,129
6,531
7,747
14,278
1,883
2,554
327
2,455
2,164
9,383
34,790
EMISSIONS BY SOURCE CATEGORY
FROM FUEL BURNING
RESIDENTIAL
1,024
534
620
1,154
251
320
45
61
311
988
3,166
COMMERCIAL &
GOVERNMENTAL
2,211
360
1,846
2,206
429
810
19
38
138
1,434
5,851
INDUSTRIAL
100
51
65
116
17
89
1
5
23
135
351
POWER PLANTS
1,184
4,159
2,253
6,412
--
--
--
1,685
631
2,316
9,912
TRANSPORTATION
1,953
982
1,350
2,332
639
648
165
199
309
1,960
6,245
INDUSTRIAL
PROCESSES
151
45
734
779
18
40
--
1
121
180
1,110
REFUSE DISPOSAL
(ALL CATEGORIES)
4,506
400
879
1,279
529
647
97
466
631
2,370
8,155
-------
Table A-8. Mean Day Emissions for Various Averaging Times
(Tons)
County or City
District of Columbia
Montgomery Co.
Prince Georges Co .
Maryland Subtotal
Arlington Co.
Fairfax Co.
Loudoun Co.
Prince William Co.
Alexandria City
Virginia Subtotal
Area Totals
Sulfur Uiox
Annual
175
189
179
368
22
17
2
43
63
147
690
h inter
281
208
202
410
49
38
3
43
65
198
889
ide
Car
Summer j Annual
90
177
198
375
4
3
-
43
62
112
577
978
602
698
1,300
282
521
57-.,
122
188
1,170
3 on Monoxide
Winter
861
530
614
1,144
248
458
50
107
165
1,028
I
3,448
3,033
Simmer
1,046
644
747
1,391
302
557
61
131
201
1,252
3,689
Particulates
.Annual V. inter
50
18
21
39
5
7
1
7
6
26
95
4o
20
24
44
8
12
1
7
. 7
55
122
Sumer
25
17
22
59
4
6
1
7
6
24
88
Ln
-------
Table A-9. GENERAL EMISSION FACTORS
(tons/unit3)
Source
Residual oil
(1,000 hp or more)
Residual oil
(1,000 hp or less)
Distillate oil
(1,000 hp or more)
Distillate oil
(1,000 hp or less)
Anthracite coal (residential)
Anthracite coal
(Commercial, Governmental)
Bituminous coal
(Residential, commercial,
Governmental )
Bituminous coal (industrial)
Natural gas
(Residential, commercial,
Governmental )
Natural gas (industrial)
Gasoline
Diesel oil
Aircraft
Open-burning dump
Municipal incinerator
Residential, commercial,
Governmental, industrial
incineration
Backyard paper burning
Gasoline evaporation
Solvent losses (dry cleaning)
SOX
0.203b
0.203b
0.024b
0.024b
0.011b
0.011b
0.019b
0.019b
0.0002
0.0002
0.004
0.020
(d)
0.0006
0.001
0.0002
0.0006
-
-
NOX
0.052
0.036
0.052
0.036
0.004
0.004
0.004
0.010
0.058
0.107
0.057
0.111
(d)
0.0003
0.001
0.0008
0.0003
-
-
Particulate
0.004
0.006
0.004
0.006
0.010C
0.025C
0.018C
0.018C
0.010
0.009
0.005
0.055
(d)
0.024
(e)
0.010
0.002
-
-
CO
Neg.
0.001
Neg.
0.001
0.025
0.025
0.025
0.002
0.0002
0.0002
1.455
0.030
(d)
0.043
0.0004
0.013
-
-
-
HC
0.0016
0.001
0.0016
0.001
0.005
0.005
0.005
0.0005
Neg.
Neg.
0.262
0.090
(d)
0.040
0.0007
0.018
0.073
0.060
1.95
Fuel oil, gasoline, and diesel fuel, 1,000 gallons; coal, tons; natural gas, 10
cubic feet; refuse, tons; dry cleaning, 1,000 people.
Dependent on sulfur content of fuel: residential oil, 2.55% S; distillate oil, 0.3% S;
anthracite coal, 0.6% S; bituminous coal, 1.0% S.
c Dependent on ash content of coal, type of firing unit, and type of control:
anthracite coal, 10.Q% A; bituminous coal, 7.0% A.
Dependent on type of aircraft, see References land 2 of this appendix.
e Dependent on type of control; see Reference 1 of this appendix.
-------
55
References for Appendix A.
1. Technical Report, Washington, D. C. Metropolitan Area Air Pollution
Abatement Activity, pp. 54-97, C-l through C-12. November, 1967
2. Ozolins, G. and Smith R., Rapid Survey Technique for Estimating
Community Air Pollution Emissions. Public Health Service, Publication
No. 999-AP-29, Environmental Health Series, USDHEW, NCAPC, Cincinnati,
Ohio, October 1966.
3. Mayer, M., A Compilation of Air Pollution Emission Factors for Com-
bustion Processes, Gasoline Evaporation, and Selected Industrial Pro-
cesses. USDHEW, PHS, DAP, TAB, Cincinnati, Ohio, May 1965.
4. Procedure for Conducting Comprehensive Air Pollution Surveys. New
York State Department of Health, Bureau of Air Pollution, Control
Services. Albany, New York. August 18, 1965.
-------
56
APPENDIX B. DIFFUSION MODEL DESCRIPTION AND RESULTS
Title I, Section 107 (a) (2) of the Air Quality Act of 1967
(Public Law 90-148, dated November 21, 1967), calls for the designation
of air quality control regions, based on a number of factors, including
"atmospheric conditions," interpreted to mean that the boundaries of air
quality control regions should reflect the technical aspects of air pol-
lution and its dispersion. Within this guideline, however, the position
has been taken that region boundaries cannot be seasonally dependant, nor
should the boundaries be based on an extreme set of circumstances which
might have a theoretical chance of occurrence. Hence the analysis of a
region's atmospheric dilution potential is largely based on mean annual
values, although summer and winter mean values are analyzed with respect
to reviewing seasonal variations in meteorology and pollutant emissions.
With the realization that the meteorological analysis would help
define tentative boundaries only and that final boundaries would be de-
veloped subsequently to reflect local governmental aspects, it was decided
that the meteorological assessment should be as unpretentious as possible.
Accordingly, the widely accepted long-term Gaussian diffusion equation,
described by Pasquill , has been applied with a few modifications to ac-
commodate certain requirements inherent to the delineation of regions.
These modifications are discussed in the next section. In summary, the
Gaussian diffusion equation is utilized to provide a geographical distri-
bution of long-period mean ground-level concentrations of SO^, CO, and
particulates. The model used has the necessary flexibility to utilize
information on emissions from both point and area-wide sources.
-------
57
The assignment of emission data on an equivalent area basis also
permits an analysis of the discrete effects from respective political
jurisdictions, utilizing respective source inventories; this technique
was used to determine the relative impact of Washington, D. C., and
Baltimore, Maryland, on each other, as discussed earlier in this report.
To maintain simplicity, all pollutant sources were assumed to be at
ground level; for CO this assumption is realistic. The same assumption
is used for major point sources of SO- and particulates, since the dis-
tances of interest are sufficiently great to obviate the source-height
effect for most receptors. The ground-level concentrations of S0? in
the vicinity of the two large point sources of SO- (northwest Montgomery
County and southeast Prince Georges Gounty) are probably over-estimated
by not considering stack height, making it necessary to discount the
results in those two instances. Also, since there is no agreement to
what constitutes an appropriate half-life and deposition rate for S0»
and particulates, respectively, these factors were not applied to the
computation of ground-level pollutant concentrations during the diffusion
model analysis. As discussed earlier in the report (page 31) and briefly
below, certain modifications have been applied to the model results to
allow comparative interpretation.
Methodology
The diffusion model used to compute long-term average pollutant
concentration distributions for respective pollutants is based on
1 ?
Pasquill's Gaussian diffusion equation , as modified by Martin . Essen-
tially, the diffusion model sums the effects (ground-level concentration)
of a number of sources (area and point) for a specified number of recep-
tors, averaged over a season or a year; the receptor points are at
-------
58
distances of 20, 30, 40, 50, 70, and 100 kilometers from a defined
central grid point for each of 16 compass directions. An average
pollutant concentration is computed for the central grid receptor
(designated in the downtown or central city area) for comparison to
air quality measurements that might be available.
The meteorological data input to the model is screened to deter-
mine the representativeness of the data. Appropriate surface wind rose
data are selected from U. S. Weather Bureau records; if necessary,
special wind data tabulations are obtained from the National Weather
Records Center (NWRC). The mean mixing depth for each region, for
each respective time period (seasonal or annual), is determined on the
basis of computed mixing depths documented by Holzworth (4,5) and recent
tabulations furnished the Meteorological Program by NWRC.
Results
A comparison of calculated concentrations of CO to air quality data
for Washington, D. C., shows reasonable agreement in relative terms, but
the model consistently underestimates the concentration in comparison to
measured values in the central urban area . As is discussed in the text
of this report, an empirically-derived correction factor has been applied
to the model output to allow comparative use of the CO data.
For SO- the model has yielded a systematic over-calculation when
compared to measured concentrations. This over-calculation is thought
to result primarily from the fact that S02, an active gas, reacts in the
atmosphere, leading to concentrations lower than those predicted by the
model. As discussed in the body of this report, a "decay factor" has
been applied to the model output to compensate for this difference. The
-------
59
decay factor used here is based on an arbitrary assumption of a six-
hour half-life for SO™. In current work on additional regions the
impact of varying assumptions on half-life is being analyzed.
For suspended particulates, the model gave unexpectedly good
results when the finite values were compared to measured concentrations.
The good correlation, however, is the result of two apparently compen-
sating limitations of the model. The source term for particulates in-
cludes total emissions; as a result, the model treats settleable
particulates as suspended and thus overestimates the concentration. At
the same time the source term does not allow for sources outside the
area under study, and the model estimates as a result do not include
the incoming or background concentration. Because of these limitations,
the model estimates for suspended particulates are interpreted in this
report only in a relative sense.
Figures B-l through B-7 present the unmodified results of the dif-
calculations for SC) and CO for the three time periods investigated and
A
for suspended particulates on an annual basis.
While limitations inherent in the model are recognized, the model
results can be appropriately modified and interpreted to provide reason-
able spatial distributions of long-term (seasonal and annual) average
pollutant concentrations, resulting from the respective source emissions
(inventory provided) originating from within a region. The reliance upon
existing jurisdictional arrangements in arriving at final region boun-
daries provides a certain geographical latitude within which the diffusion
model results can fall without significantly altering the final outcome.
-------
60
0.01
SO - ppm
Figure B-l. Estimated SO concentration; annual average^^io decay.
-------
0.01
S02 - ppm
61
Figure B-2. Estimated S02 concentration; winter average; no decay,
-------
62
SO - ppm
01
Figure B-3. Estimated SO,, concentrations; summer average; no decay,
-------
63
CO - ppm
0.2
Aerometric Data^
Station
A
B
C
D
(Alexandria)
(NIH)
(Suit land)
(CAMP)
Concentration,
ppm
5
5
5
5
Figure B-4. Estimated CO concentrations; annual average.
-------
64
0.04
CO - ppm
0.06
0.04 0
Fibure B-5. Estimated CO concentrations; winter
-------
0.10
0.04
65
0.10
Figure B-6. Estimated CO concentrations; summer average
-------
66
Suspended Particulates- g/M"
50
Figure B-7. Estimates suspended particulate concentration; annual
average; no background; no deposition.
-------
67
References for Appendix B.
1. Pasquill, F.; Atmospheric Diffusion. Van Nostrand Co., New York,
N. Y. page 19(T I96T
2. Martin, D. 0.; A general atmospheric diffusion model sources,
Paper No. 68-148 presented at the Air Pollution Control Assoc-
iation's 61st Annual Meeting, St. Paul, Minnesota. June 23-27,
1968.
3. Turner, D. B.; Workbook of Atmospheric Dispersion Estimates.
PHS Publication No. 999-AP-26, 84 pp. National Center for Air
Pollution Control, Cincinnati, Ohio. 1967.
4. Holzworth, G. C.; Estimates of mean maximum mixing depths in
the contiguous United States, Mon. Weather Rev. 92: pp. 235-
242. May, 1964.
5. Holzworth, G. C.; Mixing depths, wind speeds and air pollution
potential for selected location in the United States, J. Appl.
Meteor. 6; pp. 1039-1044. December, 1967.
6. Technical Report, Washington, D. C., Metropolitan Area Air Pol-
lution Abatement Activity. National Center for Air Pollution
Control, DHEW. Cincinnati, Ohio, page 152. 1967
-------
68
APPENDIX C. DEMOGRAPHIC DATA
This appendix consists of tables and figures showing various
parameters of Washington, D. C., urban area. Some of these data are
referred to in the body of this report, and some are not. It all has
relevance to the National Capital Area and is included in this report
for possible future use.
-------
69
Table C-l . General Information on Counties in the
Washington, D.C. Air Quality Control Region"
County
County Seat
Basic Trading Area
Major Trading Area
Land Area (Sq. Miles)
Population (1950)
(1960)
est. (1968)
Households (1968 est.)
Total Retail Trade 1966
($1000)
Shopping Goods Sales 1966
($1000)
Food Store Sales 1966
($1000)
Drug Store Sales 1966
($1000)
Passenger Car Registrations
Total Wholesale Trade
(1963) ($1000)
Manufactures:
Total Employees
Value Added ($1000)
Agriculture:
Number of Farms
Total Value of Products Sold
($1000)
District of
Columbia
Washington
Washington
Washington
61
802,178
763,956
815,000
269,000
1,750,425
408,597
271,644
97,825
218,760
2,437,765
22,262
256,813
None
N.A.
Montgomery
Rockville
Washington
Washington
496
164,401
340,928
455,000
122,300
786,386
148,546
186,199
25,059
211,713
433,713
7,091
61,124
737
10,036
Prince
Georges
Upper
Marlboro
Washington
Washington
484
194,182
357,395
595,000
155,800
736,215
123,332
174,792
31,915
223,639
387,962
9,166
98,127
1,087
6,858
Arlington
Fairfax
Washington
Washington
26
135,449
163,401
188,000
62,700
417,053
98,513
77,465
19,829
147,680
350,595
1,470
12,820
8
72
-------
70
Table C-2 . General Information on Counties in the
Washington, D.C. Air Quality Control Region
County
Fairfax
Loudoun
Prince
William
County Seat
Basic Trading Area
'tajor Trading Area
^and Area (Sq. miles)
Population (1950)
(1960)
est. (1968)
households (1968 est.)
Total Retail Trade 1966
($1000)
Shopping Goods Sales 1966
($1000)
Food Store Sales 1966
($1000)
Drug Store Sales 1966
($1000)
Passenger Car Registrations
Total Wholesale Trade
(1966) ($1000)
!lanufactures :
Total Employees
Value Added ($1000)
Agriculture:
Number of Farms
Total Value of Products Sold
($1000)
^airfax
Washington
Washington
399
96,611
248,897
391,000
99,700
296,461
65,331
90,575
18,742
90,420
117,618
6,625
60,786
428
2,889
Leesburg
Washington
Washington
517
12,826
12,959
32,000
8,400
38,411
2,505
9,420
2,019
8,600
6,330
294
2,526
947
10,761
Manassas
Washington
Washington
347
22,612
50,164
92,500
21,900
81,524
8,536
19,529
4,113
9,940
5,143
380
3,891
479
3,028
-------
71
Table C-3. General Information on Major Incorporated Municipalities
in the Washington, D.C. Air Quality Control Region 1
City
Rockville Hyattsville
SMSA
Falls Church
County
Basic Trading Area
lajor Trading Area
tenally City Rating
Economic Activity Code
Population: 1960
est. 1968
households (est. 1968)
Total Retail Trade
(1966) ( $1000)
Shopping Goods Sales
(1966) ($1000)
Total Wholesale Trade
Manufactures :
Total Employees
Value Added ($1000)
Montgomery
Washington
Washington
3S
Dr - Commuter
& Retail
26,090
37,000
9,000
108,780
13,173
36,420
1,227
11,409
Prince Georges
Washington
Washington
4S
Dr- Commuter
& Retail
15,168
17,700
5,200
69,000
2,000
22,529
294
2,670
N.A.
Washington
N.A.
Government
2,076,610
2,720,000
779,300
4,489,162
913,081
2,058,972
22,262
256,813
N.A.
Washington
Washington
3S
Dr - Commuter
& Retail
10,192
12,500
3,500
79,465
7,399
22,869
241
1,848
-------
72
TABLE C-4 .
GENERAL INFORMATION ON MAJOR INCORPORATED
MUNCIPALITIES IN THE WASHINGTON D.C. AIR QUALITY CONTROL REGION1
City
County
Basic Trading Area
Major Trading Area
Ranally City Rating
Economic Activity Code
Population: 1960
] est. 1968
Households (est. 1968)
Total Retail Trade
(1966) ($1000)
Shopping Goods Sales
(1966) ($1000)
Total Wholesale Trade
Manufactures:
Total Employees
Value Added ($1000)
WASHINGTON ALEXANDRIA FAIRFAX
N.A.
Washington
Washington
Government
763,956
815,000
269,000
1.750.A25
408,597
2,437,765
22,147
256,813
N.A.
Washington
Washington
3-SS
DR - Commuters
& Retail
91,032
115,000
36,100
229,965
47,959
103,623
3,336
33,708
N.A.
Washington
Washington
None
13,585
24,000
6,000
73,257
2,363
8,420
14
72
-------
73
TABLE c-5 •
1950-1966
TOTAL CAR REGISTRATION BY JURISDICTION FOR WASHINGTON SMSA2
(Excluding Loudoun and Prince William Counties)
Year
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
Mont.
County
66,757
75,475
80,385
87,223
95,327
107,757
116,045
124,474
131,886
144,049
157,160
166,984
178,607
192,538
207,390
223,148
Pr. Geo.
County
65,968
75,397
83,088
88,426
96,113
107,297
114,051
120,466
127,360
139,873
151,166
160,279
174,668
193,923
214,618
238,298
Arl.
County
40,644
42,287
43,928
45,514
48,312
53,259
56,511
59,218
62,624
64,774
67,957
71,334
74,534
77,469
79,411
83,007
82,199
Fairfax
County
42,222
49,395
57,997
65,079
68,239
74,051
81,958
89,342
98,182
109,287
119,603
131,675
141,039
Falls
Church
3,280
3,462
3,657
3,864
3,912
3,908
4,194
4,446
4,845
5,183
5,611
Dist. of
Columbia
206,378
202,254
204,766
203,545
206,786
216,168
207,262
205,077
204,647
208,169
213,395
215,633
218,284
227,030
235,760
243,782
258,954
-------
74
TABLE C-6.
1950-1966
PASSENGER CAR REGISTRATION BY JURISDICTION FOR WASHINGTON SMSA 2
(Excluding Loudoun and Prince William Counties)
Year
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
Mont.
County
59,601
67,099
71,870
78,158
85,333
96,323
103,580
111,325
118,102
129,306
141,189
150,489
161,459
174,048
187,148
200,337
Pr. Geo.
County
58,144
66,910
72,898
77,238
83,713
95,525
98,878
104,954
110,939
121,321
131,676
138,890
151,507
167,675
186,369
207,112
Arl.
County
38,114
39,461
42,311
44,653
47,652
52,518
55,492
58,324
61,465
63,564
66,778
70,157
73,068
75,796
77,026
81,259
80,310
Dist. of
Columbia
167,109
163,081
164,858
163,615
167,543
179,691
171,617
170,698
170,980
174,618
179,405
181,986
185,011
192,659
200,270
209,618
217,026
-------
75
Table C-7. New housing starts by 5-year periods and per cent increase.
Jurisdiction
Montgomery Co.
Prince Georges Co.
District of Columbia
Alexandria City
Arlington Co.
Fairfax Co.
Loudoun Co.
Prince William Co.
dumber of Housing Starts
1950-1954
28,122
25,135
22,480
4,444
10,400
20,769
604
163
1962-1966
26,527
72, 787
33,777
12,734
10,323
41,558
2,971
10,107
Percentage change,
1962-66 over 1950-54.
-5.6
+190
+50
+164
0
+100
+392
+6,100
-------
,TABLE C-8 . 1930-1960 RANKING OF 20 LARGEST METROPOLITAN AREAS
Percent Change
Population 1950- 1940- 1930-
Rank Area
1. New York-N.E. New Jersey
2. Chicago-N.W. Indiana
3. Los Angeles-Long Beach
4. Philadelphia, Pa.
5. Detroit, Michigan
6. Boston, Massachusetts
7. San Francisco-Oakland
8. Washington, D. C.-Md.-Va.
9. Pittsburgh, Pa.
10. St. Louis. Mo. -111.
11. Cleveland, Ohio
12. Baltimore, Md.
13. Houston, Texas
14. Minneapolis-St. Paul, Minn.
15. Dallas, Texas
16. Milwaukee, Wisconsin
17. Cincinnati, Ohio-Ky
18. Buffalo, New York
19. Seattle, Everett, Wash.
20. Atlanta, Georgia
TOTALS
1960
14,759,429
6,794,461
6,742,696
4,342,897
3,762,360
2,589,301
2,783,359
2,001,897
2,405,435
2,060,103
1,796,595
1,727,023
1,243,158
1,482,030
1,083,601
1,194,290
1,071,624
1,306,957
1,107,213
1,017,188
61,259,097
1950
12,911,994
5,586,096
4,367,911
3,671,048
3,016,197
2,410,572
2,240,767
1,464,089
2,213,236
1,719,288
1,465,511
1,405,399
806,701
1,151,053
743,501
956,948
904,402
.1,089,230
844,572
726,989
49,695,504
1940
11,660,833
4,890,674
2,916,403
3,199,367
2,377,329
2,209,608
1,461,804
967,985
2,082,536
1,464,111
1,267,270
1,139,529
528,961
967,367
527,145
829,639
787,044
958,487
593,734
558,842
41,388,658
1930
10,859,433
4,733,777
2,327,166
3,137,040
2,177,343
2,168,566
1,347,772
672,198
. 2,023,269
1,387,075
1,243,129
1,036,753
359,328
882,226
458,629
777,621
756,281
911,737
515,378
360,000
38,134,761
i
60 50 40
14.3 10.7 '7,4
21.6 14.2 3.3
54.4 49.8 "25.3
18.3 14.7 2.0
24.7 26.9 9.2
7.4 9.1 1.9
24.2 53.3 8.5
35.9 51.3 44.0
8.7 6.3 2.9
19.8 17.4 5.6
22.6 15.6 1.9
22.9 23.3 9.9
54.1 52.5 47.2
28.8 19.0 9.6
45.7 41.0 14.9
24.8 15.3 6.7
18.5 13.0 4.1
20.0 13.6 5.1
31.1 42.2 15.2
39.9 30.1 55.2
25.9 26.0 14.0
Av . Av . Av .
Source: U.S. Census of Population, 1930-1960.
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77
References for Appendix C.
1. Rand McNally Commercial Atlas, and Marketing Guide. 99th ed.
1968.
2. Statistics - Washington Metropolitan Area. Metropolitan Washington
Council of Governments, page 146, January, 1968.
3. Statistics - Washington Metropolitan Area. Metropolitan Washington
Council of Governments, pp. 138-9, January, 1968.
4. Statistics - Washington Metropolitan Area. Metropolitan Washington
Council of Governments, page 35, January, 1968.
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